The present invention relates to a vehicle stability augmentation system in conjunction with a hydraulic and electric power steering control system for a motor vehicle and more particularly, for controlling the steering angle of the wheels to be steered of the vehicles in accordance with the state of movement of the motor vehicle to which the system is applied.
Various types of steering apparatuses for motor vehicles have been developed. Such examples include electric motor-driven pump-type power steering systems. The flow rate of the oil delivered from the oil pump is controlled to allow a driver to operate a steering wheel with optimum steering force.
The oil pump and motor are always driven even when power assist is unnecessary. Thus, the system operates at low efficiency.
An electric power steering system in which an electric motor is connected to a steering shaft or steering rack, is an efficient demand type power steering. However, it is difficult to ensure fail-safe operation due to possible malfunction such as motor, gear or screw lock.